This invention relates to a method of treating schistosomal infestations by both adult worms and eggs-miracidia, particularly residing in the veins, venules and nearby tissues either of the bladder and ureters, or of the colo-rectal regions of the intestines, by iontophoresis.
Known in the art is the systemic chemotherapy of schistosomiasis by intravenous or intramuscular administration of antischistosomal drugs such as trivalent or pentavalent antimony compounds or, more recently, by oral administration of antischistosomal drugs such as niridazole, metrifonate, oxamniquine and praziquantel.
Illustrative examples of trivalent antimony compounds used in the treatment of schistosomiasis are salts with organic acids such as: antimony potassium or sodium tartrate, sodium antimonyl gluconate, antimony sodium thioglycollate, antimony thioglycollamide, sodium antimony dimercaptosuccinate, stibophen, i.e. pentasodium antimony bis(catechol-3,5-disulphonate) heptahydrate.
The pentavalent antimony compounds are typified by sodium stibogluconate even if other salts thereof with organic acids can be used. The antimony compounds are slowly, irregularly and only partially absorbed from the intestinal tract and are therefore administered by injection. They are known for their toxic effects. The toxicity of antimony, closely resembling that of arsenic, may manifest as intestinal irritation, chemical pneumonia, cardiac dysfunction, liver damage, joint and muscle pain and vascular collapse.
The advent of more easily administered, effective and generally less toxic antischistosomal drugs, has resulted in the virtual abandonment of the trivalent antimony compounds.
Niridazole was the first of the effective orally-administered antischistosomal drugs but it has some marked toxic effects as hallucinations, convulsions, liver damage, destruction of erythrocyte and changes in the electrocardiogram. It has one side effect which makes it pertinent for the object of the present invention, namely a strong anti-inflammatory action.
Metrifonate is another effective orally-administered antischistosomal drug, an organophosphate especially effective in the treatment of infections caused by S. mansoni and S. hematobium resulting in a 90% reduction in egg counts and a 40-90% cure rate. Side effects appears when the patient comes into contact with other organophosphates, such insecticides and there are cumulative and occasionally disastrous episodes of poisoning.
Another orally administered antischistosomal drug is oxamniquine. This drug is effective only in the treatment of S. mansoni infections and displays a blatant sexual discrimination, only male worms being affected. The treatment results in a 90-95% reduction in egg counts and a cure rate of 70-100%.
The most valuable of the presently known antischistosomal drugs seems to be praziquantel. It is effective against all five schistosomal species and results in a 95% reduction in egg counts and 85% cure rate. PG,4
Systemic chemotherapy of schistosomiasis although very successful in reducing the intensity of infestations, results in a failure rate of 5-60% (depending upon the source of reports) in terms of actually curing (obliterating) the disease.
Even with the recent, orally administered antischistosomal drugs effecting dramatic reductions in the infestations, treated individuals although often well in themselves, are still spreading infection from residual adult worms laying eggs which are transmitted via the bladders or intestine to outside bodies of water, allowing the propagation of schistosomal infestations.